1. Field of the Invention
The present invention relates to fuel vapor adsorption filters, and in particular to fuel vapor adsorption filters that have a filter body and a frame surrounding the circumference of the filter body. The filter may be mounted within an intake air channel connected to an engine, e.g., an internal combustion engine, via the frame. The filter body may adsorb a fuel vapor within the intake air channel when the engine has stopped.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 2003-42017 teaches a known fuel vapor adsorption filter. As shown in FIGS. 10(A), 10(B), and 10(C), a fuel vapor adsorption filter of this publication has a filter body 92 and a frame 94 surrounding the filter body 92. During the operation of an engine, the filter body 92 may permit intake air to pass through the filter body 92. When the engine has stopped, the filter body 92 may adsorb a fuel vapor within the intake air channel. The filter body includes an adsorption agent 92b made of activated carbon granules, a non-woven fabric 92c encasing and holding the adsorption agent 92b, and a net 92m made of resin and serving to protect the non-woven fabric 92c from any backfire flames produced by the engine. As shown in FIG. 10(A), injecting a resin into a mold 96, while an edge portion 92f of the filter body 92 is inserted into the mold 96, may produce the frame 94. In this way, the frame 94 is integrated with the filter body 92 at the same time that the frame 94 is molded. As shown in FIG. 10(C), a plurality of mounting holes 94h are formed in the frame 94 and are arranged in a circumferential direction. Pins 98p of an air cleaner housing 98 may be respectively inserted into the mounting holes 94h. The head portions of the pins 98p may then be heat-crimped, mounting the fuel vapor adsorption filter to the air cleaner housing 98.
However, in the case of the fuel vapor adsorption filter of the above publication, in order to mold the frame via an injection molding process, the edge portion 92f must be positioned between mating surfaces 96a and 96b of the mold 96. Therefore, the adsorption agent 92b made of activated carbon granules cannot be positioned at the edge portion 92f. This means that a range exists where no adsorption agent 92b is provided for a certain width inside of the frame 94 (i.e., the edge portion 92f of the filter body). As noted previously, the filter body 92 is primarily made of non-woven fabric 92c in order to permit the passage of intake air. Therefore, the edge portion 92f of the filter body 92 may permit the passage of air. However, this may result in the potential leakage of fuel vapor through the edge portion 92f. 
In addition, because the frame 94 of the known filter is molded by an injection molding process, a different material than the material used for the filter body 92 is required for the frame 94. This may result in a problem of increased manufacturing costs.